Rapid post-fire re-assembly of species-rich bryophyte communities in Afroalpine heathlands

Questions In some fire-prone ecosystems, bryophytes play a crucial role by providing the surface fuel that controls the fire return interval. Afroalpine heathlands are such an ecosystem, yet almost nothing is known about the bryophytes in this system. We do not know the level of species richness, or if there is a successive accumulation of species over time, or if some species are adapted to specific phases along the successional gradient, for example early-successional species sensitive to competition. Location Afroalpine heathlands in Ethiopia. Methods We made an inventory of all bryophytes in 48 plots of 5 m × 5 m, distributed along a chronosequence from 1 to 25 years post fire. The heathlands are located between 3500 m and 3800 m a.s.l. and are managed by traditional pasture burning with fire intervals of 8–20 years. Results We found in total 111 taxa of bryophytes. Post-fire mortality was almost 100%. The youngest plots had only a few cosmopolitan species often found after fire. Initially, species richness increased monotonically while starting to level off around 15 years after fire, when many plots had around 30 species and a high cover of Breutelia diffracta, which is a key ground-living species, important as surface fuel. Most species were found with sporophytes, a pattern even stronger for the most frequent species. Conclusions Interestingly, bryophyte diversity is already remarkably high by only 15 years after total eradication. The relatively slow accumulation of species in the first years after fire suggests that dispersal in space, and not time, is the major mechanism by which sites regain their diversity (i.e. spore banks play a smaller role than colonization of wind-borne spores). This indicates that the high species richness is built up through colonization from surrounding heathlands, and perhaps also from higher-altitude alpine grasslands and lower-altitude forests, and that the bryophyte diversity in this system is maintained by the traditional fire and grazing management

Projectile breakup dynamics for 6^{6}Li + 59^{59}Co: kinematical analysis of α\alpha-dd coincidences

A study of the kinematics of the $\alpha$-$d$ coincidences in the $^{6}$Li + $^{59}$Co system at a bombarding energy of $E_{lab} = 29.6$ MeV is presented. With exclusive measurements performed over different angular intervals it is possible to identify the respective contributions of the sequential projectile breakup and direct projectile breakup components. A careful analysis using a semiclassical approach of these processes provides information on both their lifetime and their distance of occurrence with respect to the target. Breakup to the low-lying (near-threshold) continuum is delayed, and happens at large internuclear distances. This suggests that the influence of the projectile breakup on the complete fusion process can be related essentially to direct breakup to the $^6$Li high-lying continuum spectrum. %Comment: Revised version including new Fig.3 and Fig.4 with new CDCC calculations. Accepted for publication at Eur. Phys. Jour. A. 11 pages, 6 figure

Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities

8 páginas, 2 tablas, 2 figuras.1. Many Mediterranean plant species persist after fire because their seeds are protected from the heat of the fire (e.g. hard-coated seeds, serotinous cones), thus permitting rapid post-fire recruitment. For simplicity, this trait will hereafter be called P and its two possible phenotypes P+ (seeder) and P– (non-seeder). 2. Because P+ appears in a narrow taxonomic spectrum and confers persistence under high fire frequencies, we test the extent to which communities with different fire histories have different phenotypic and phylogenetic structures. Specifically, we compare coastal vegetation growing in a warm and dry Mediterranean climate subject to high fire frequency (HiFi vegetation) with montane vegetation subject to a subhumid climate where fires are rare (LowFi) under the hypothesis that P+ species will be over-represented in HiFi communities, thus producing phenotypic and phylogenetic clustering. 3. Trait conservatism on P is evaluated by testing the presence of a phylogenetic signal, phenotypic clustering is tested by correlating co-occurrence and phenotypic distance matrices, and the phylogenetic structure is evaluated by testing whether the phylogenetic distances between species in each community are different from those expected by chance. 4. The results suggest that: (a) P is a strongly conserved trait; (b) co-occurring species have similar P phenotypes (phenotypic clustering); and (c) the phylogenetic structure in HiFi vegetation is significantly clustered while LowFi vegetation tends to be overdispersed. 5.Synthesis: Fire is a strong driving force in assembling HiFi communities while other forces, such as competitive interactions, are the main assembly mechanisms in LowFi communities. This result supports the role of recurrent disturbances as filters driving phylogenetic community structure.We thank C. Webb and S. Kembel for their help in the use of the Phylocom software and P. García-Fayos and G. Segarra-Moragues for helpful comments on the local flora. P. Clarke, P. Vesk and C. Romero provided valuable comments on the manuscript and J. A. Pascual produced the map for Fig. 1. This work has been partially financed by the Spanish Government project PERSIST (CGL2006-07126/BOS). CEAM is supported by Generalitat Valenciana and Bancaixa.Peer reviewe

Bark thickness and fire regime

Bark is a vital and very visible part of woody plants, yet only recently has bark characteristics started to be considered as key traits structuring communities and biomes. Bark thickness is very variable among woody plants, and I hypothesize that fire is a key factor selecting for a thick bark, and thus, at the global scale, a significant proportion of the variability in bark thickness is explained by the variability in fire regimes. Previous research has focused on the importance of bark thickness mainly in surface-fire regimes; here I generalize this idea and present a conceptual framework to explain how the different drivers that affect fire intensity have shaped bark thickness, in conjunction with other plant traits. I first review methods used to study bark thickness and then provide examples of bark thickness patterns from a wide range of ecosystems subject to different fire regimes (understorey fires, grass-fuelled surface fires, grass-fuelled crown fires and infrequent fires). There are some fire regimes that select for thick barks, while some only in the base of the trunk (e.g. understorey fires), others select for a thick bark on the whole plant (e.g. grass-fuelled crown fires). There are also fire regimes in which allocating resources to a thick bark is not adaptive (e.g. woody-fulled crown fires). Fire regime can explain a large proportion of the variability of bark thickness at the global scale, and thus, this trait varies across ecosystems in a predictable manner; however, the current paucity of data limits a fully accurate analysis. © 2014 The Authors.This research has been performed under the framework of the TREVOL project (CGL2012-39938-C02-01) from the Spanish government.Peer Reviewe